Wireless systems, such as PCS and cellular systems, typically include a centralized mobile switching center (MSC) responsible for call routing, user location tracking, billing information, and connectivity with other communication systems. The MSC is connected to base station controllers (BSCs), each of which supports one or more base transceiver stations (BTSs). Each BTS supports one or more cells or cell sectors based on the number and configuration of antennas supported by the BTS. A customer communicates with the wireless system through a wireless unit, such as a radio telephone, when the telephone is within the coverage range of a cell. When a call is placed, a circuit-switched connection is established from the telephone, through the BTS and BSC, to the MSC. The MSC determines the destination and, if the destination is to another telephone within the wireless system, establishes a circuit-switched connection to the destination telephone. If the destination is outside of the wireless system, the MSC routes the call to a service provider for the outside destination.
A key component in any wireless communication system is the antenna forming the edge contact between wireless subscribers and the remaining system. Typically, each antenna is designed to provide sectored or directional coverage over a portion of the region around the BTS. Each subscriber transceiver, such as a radio telephone, has an omnidirectional antenna. When the radio telephone is within the sector established by a BTS directional antenna, a wireless link is established between the directional BTS antenna and the omnidirectional radio telephone antenna. Downlink information is transmitted from the directional antenna into the sector and is received by the radio telephone. Uplink information is transmitted in a uniform coverage area around the radio telephone and is received by the BTS directional antenna.
There are several problems associated with the conventional wireless scheme of using directional access antennas and onmidirectional telephone antennas. First, omnidirectional antennas are often within the overlapping coverage area of multiple sectors. Second, the omnidirectional broadcasts from telephones may interfere with transmissions to and from nearby telephones. Third, telephones have no control over which directional antenna establishes the communication link. What is needed is to provide an improved interface between wireless subscriber units such as radio telephones and the point at which these units connect to a wireless communication system.